1. Field of the Invention
The present invention relates to vacuum cleaners and, more particularly, to an improved cyclone separator for a central vacuum cleaning system.
2. The Prior Art
Cyclone separators for central vacuum cleaning systems have long been known in the prior art. Typically, cyclone separators have a cylindrical casing with a suction fan in the upper end thereof. In some types of cyclone separators, a straight cylindrical cyclone tube extends downwardly into the casing from the inlet to the suction fan. For example, see U.S. Pat. No. 2,684,125 and U.S. Pat. No. 3,308,609.
In the operation of cyclone separators of this type, incoming dust-laden air passes through a tangential air inlet and then downwardly in a circular path through a straight passageway provided between the exterior of the cyclone tube and the inner wall of the housing. The circulating action of the air causes centrifugal separation of the dirt particles, which are collected in a dirt receptacle placed below the cyclone tube. The air is then exhausted through the center of the cyclone tube and through the suction fan to an air exhaust outlet.
With this type of cyclone separator, it has been observed that some of the dust carried with the inlet air is drawn through the cyclone tube by the suction fan and exhausted therefrom before it has a chance to be separated from the air. This, of course, is undesirable because it causes unsightly pollution and a dirty appearance in the exhaust area.
Attempts have been made to overcome this disadvantage by restricting the lower end of the air passage between the cyclone tube and the casing wall. See, for example, U.S. Pat. No. 2,943,698. This type of restriction forces the air to squeeze through the restricted opening so that it will be forcefully ejected into the dust receptacle below the cyclone tube.
However, restricting the lower end of the air passage between the cyclone tube and the casing wall may be somewhat disadvantageous since it will tend to decrease the centrifugal separation of dirt particles that would otherwise occur. In particular, the incoming dirt-laden air will be squeezed as it moves downwardly in the passage thus precluding some of the centrifugal action that would otherwise occur as the air travels in a circular path.
Accordingly, what is needed is a cyclone separator-type vacuum cleaner that is designed to maximize the centrifugal separation of dirt particles from the incoming air while at the same time directing the circulating air so that it will not be prematurely withdrawn by the suction fan before the dust has had a chance to fully settle out.